206398721 has 2 divisors, whose sum is σ = 206398722. Its totient is φ = 206398720.

The previous prime is 206398679. The next prime is 206398733. The reversal of 206398721 is 127893602.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 186049600 + 20349121 = 13640^2 + 4511^2 .

It is a cyclic number.

It is not a de Polignac number, because 206398721 - 2²² = 202204417 is a prime.

It is not a weakly prime, because it can be changed into another prime (206398421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 103199360 + 103199361.

It is an arithmetic number, because the mean of its divisors is an integer number (103199361).

Almost surely, 2^206398721 is an apocalyptic number.

It is an amenable number.

206398721 is a deficient number, since it is larger than the sum of its proper divisors (1).

206398721 is an equidigital number, since it uses as much as digits as its factorization.

206398721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36288, while the sum is 38.

The square root of 206398721 is about 14366.5834839046. The cubic root of 206398721 is about 590.9748520329.

The spelling of 206398721 in words is "two hundred six million, three hundred ninety-eight thousand, seven hundred twenty-one".